Mpp10p, a new protein component of the U3 snoRNP required for processing of 18S rRNA precursors.
We have used the yeast, Saccharomyces cerevisiae, as a model system to identify a new protein component of the U3 small nucleolar ribonucleoprotein (snoRNP) and to study its role in pre-rRNA processing. Mpp10p, which we have cloned and characterized from humans, mice and yeast, is a 110 kDa protein in yeast. Antibodies to it immunoprecipitate the U3 snoRNA, indicating that it is a U3 snoRNP component. MPP10 is an essential gene. Depletion of Mpp10p by repression of MPP10 expressed from a conditional promoter causes slow growth. Analysis of pre-rRNA processing in the depleted cells indicates that Mpp10p is required for processing at the 3 U3 snoRNA-dependent sites in the pre-rRNA (A0, A1, A2). Truncations of terminal charged domains create Mpp10 proteins that confer slow growth at 30 degrees C and/or at 22 degrees C. Analysis of pre-rRNA processing in these mutants indicates a deficiency in processing at only two of the U3 snoRNA-dependent sites in the pre-rRNA (A1 and A2). Therefore truncated Mpp10 proteins are able to separate the function of the U3 snoRNP into a requirement for it in distinct processing events.
Baserga
S J
SJ
Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, CT 06520-8040, USA.
Agentis
T M
TM
Wormsley
S
S
Dunbar
D A
DA
Lee
S
S
D000818:Animals; D006801:Humans; D051379:Mice; D016297:Mutagenesis, Site-Directed; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D012322:RNA Precursors / Q000378:metabolism*; D012323:RNA Processing, Post-Transcriptional; D012337:RNA, Ribosomal, 18S / Q000378:metabolism*; D012261:Ribonucleoproteins / Q000235:genetics / Q000378:metabolism*; D017411:Ribonucleoproteins, Small Nuclear / Q000378:metabolism*; D012441:Saccharomyces cerevisiae
C111101:MPHOSPH10 protein, human; D010750:Phosphoproteins; D012322:RNA Precursors; D012337:RNA, Ribosomal, 18S; D012261:Ribonucleoproteins; D017411:Ribonucleoproteins, Small Nuclear